Carbonate Petrophysical Parameters Derived From 3D Images

Carbonate rocks are extremely diverse and their pore spaces complex and heterogeneous. Large uncertainties in the petrophysical properties of carbonates are due to wide variations in pore type, pore shape and interconnectivity. Petrophysical properties such as acoustic velocity, permeability, and resistivity are directly correlated to the amount and type of porosity, the dominant feature size, and the interconnectivity of different porosity types. Accurately measuring these attributes requires the quantitative 3D analysis of the pore structure of carbonates. In this article we describe the imaging and analysis of two types of carbonate core: a set of vuggy, recrystallized dolostones and a set of oomoldic limestones. The structure and topology of the pore space is accurately determined via micro-CT analysis and the porosity consistent with experimental data. Acoustic velocity-porosity, pore connectivity, and porosity permeability relationships are derived directly on the image data via numerical simulation and compared with measured data on the same rock. Acoustic velocity:porosity trends are good. Pore structural properties (pore size, aspect ratios, pore and throat shape and connectivity) are determined. The correlations between pore geometry and topology and elastic and flow properties can be directly probed in a systematic manner. Three dimensional imaging and analysis of carbonate core material can provide a basis for more accurate petrophysical modeling and improve carbonate reservoir characterization.